Is there a way, or planned a way, to have versioning as part of the
protocol itself? For example, it could be possible for the PC side to
request the target for the version used.

Or the target could be allowed to use various versions of the procotol in
parallel, and the PC side would know, for example by looking at the
message header, which version the message belongs to. This would make
really good sense if different parts of the target is delievered from
different vendors, each implementing different versions of the protocol
(you can't expect everyone to upgrade at the same time).